A radar device transmits transmission pulses and receives pulse signals reflected by a target to measure a distance from the target based on the time differences between the transmission pulses and reception pulses.
Japanese Patent Application Laid-Open No. 2002-374181 discloses a radio frequency receiver. In the radio frequency receiver, after passing an input modulated signal through a band-pass filter, a sample-and-hold circuit samples the signal using a subsampling frequency, which is sufficiently lower than a radio carrier frequency but has a bandwidth twice as a payload bandwidth, to digitalize the signal. The digitalized signal is supplied to two digital mixers and a common-mode component (I) and an orthogonal component (Q) of the payload are generated.
Japanese Patent Application Laid-Open No. 8-213944 discloses, in FIG. 1, an analog-digital converting means having a clock, a sample-and-hold circuit and an analog-digital converter.
Japanese Patent Application Laid-Open No. 10-135869 listed below discloses a receiving device. The receiving device controls to set a time window, which includes all detected peak values that exceed a predetermined threshold value, in each symbol period. Only during the time windows, sampling pulses are sequentially output to an analog sample-and-hold circuit to sample and hold correlation output signals. Then, after the time window ends, the receiving device also controls a switch to sequentially input each sampling value to an A/D converter and convert the values into digital signals.